Knots have been used for centuries in flexible or pliable elongated members such as ropes, cords, twine, laces and the like for fastening or holding fast the elongated members either to another elongated member or another structure.
People learn many different knots over time. The act of tying ones shoes, for example, involves a number of different knotting elements specifically an overhand knot with locking tuck on a bight (or two bites as necessary). All that is needed is for one loose end of the lace to double back through one of the bites and the knot becomes tangled when one tries to untie it.
Anyone who has had the experience of working with knots has also suffered the frustration of trying to untie a knot that has become tangled. A tangled knot can be defined as; “to seize and to hold in as if in a snare, or to unite or to knit together in intricate confusion”. And anyone who has experienced a tangled knot can testify that, all too often, the harder one pulls on the ends of the elongated member, the tighter the knot becomes.
At that point, one must simply focus on elements of the knot itself to loosen the entanglements, often referred to as picking the knot. The problem here is that the knot, by that time, resembles a monolithic mess that no finger or picking device can successfully access from outside the knot.